As a technology that mounts a millimeter wave radar on a vehicle and performs automatic braking operation based on a distance to a front obstacle, Patent Document 1 discloses the following configuration: “When a predicted time to be required until the distance between an object and an own vehicle as derived based on a relative distance and a relative speed between the object and the own vehicle has decreased beyond a preset value, step-by-step braking control is performed by automatically and gradually increasing a braking force or a braked deceleration in a plurality of stages in time series. As a stage still earlier than the first one of the plurality of stages, for example, a caution stage in which the braking force or braked deceleration is still smaller than that in the first stage is included. In this caution stage, braking is performed using an auxiliary brake” (extracted from the Abstract).